German Patent 44 05 776 and corresponding U.S. Pat. No. 5,518,039 (Haeussler et al.) discloses a rotational leno selvage forming device having a rotationally driven leno disk that forms the rotor of an electric motor to provide a direct electromagnetic drive for the leno disk. The leno disk has two thread guides arranged symmetrically relative to the center axis of the leno disk, whereby two leno threads respectively supplied from two leno thread spools are respectively guided through the two thread guides. The rotation of the leno disk opens and closes a leno shed for leno-binding the weft threads along the edge of the woven web.
With regard to the arrangement of the leno device, the above mentioned German Patent suggests that it is advantageous to arrange the leno disk with its rotation axis parallel to the weft insertion direction, and with the leno disk spaced away from the if binding point of the web at a necessary minimum distance. The electric motor, of which the leno disk forms the rotor, is for example an electrically actuatable servo motor or stepper motor or the like, that operates according to generally known principles using a radial magnetic flux. The motor windings are carried by the stator while magnets are arranged on the outer circumference of the rotor in a respective partial circular manner. The stator of the motor is received in a housing-like carrier member, which forms a holder for connecting the leno device to the loom.
While the known leno device disclosed in the above mentioned German and U.S. Patent references has been found to be very effective for achieving its stated objects, it has additionally been found to be desirable to provide an improved bearing support for the leno disk forming the rotor of the motor, to provide an improved enclosure whereby the bearing support arrangement and the overall drive is enclosed or shielded from external contaminants such as thread clippings, fly lint and the like, and to provide a system for accurately sensing and measuring the respective angular position of the leno disk at all times. The above mentioned German and U.S. Patent references do not disclose the specific details of the bearing support arrangement for the leno disk and for determining its rotational or angular position, especially in the case of applications in which the leno device is operated with the leno disk rotating in reversing opposite directions.